Messages in this thread | | | Date | Fri, 17 Dec 2010 13:35:07 -0500 | From | Vivek Goyal <> | Subject | Re: kdump broken on 2.6.37-rc4 |
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On Fri, Dec 17, 2010 at 10:21:24AM -0800, Yinghai Lu wrote: > On 12/17/2010 10:02 AM, Vivek Goyal wrote: > > On Fri, Dec 17, 2010 at 09:56:42AM -0800, H. Peter Anvin wrote: > >> On 12/17/2010 09:01 AM, Vivek Goyal wrote: > >>> On Thu, Dec 16, 2010 at 07:58:48PM -0800, Yinghai wrote: > >>>> Please don't do that to 64 bit > >>>> > >>>> My big system with 1024g memory and a lot of cards with rhel 6 to make kdump work must have crashkernel=512m and second kernel need to take pci=nomsi > >>>> > >>> > >>> I agree here that we should not do it for 64 bit. > >>> > >>> - Just because we need it for 32 bit does not mean we should limit it for > >>> 64bit. And we do want to have the capability to boot the kernel from as > >>> high memory as possible so creating another aritificial limit is counter > >>> to that. > >>> > >>> - I would not worry too much about backward compatibility and allow > >>> booting 32bit kernel till 768MB. The reason being that most of the > >>> distros use same kernel for crash dumping as regular kernel. Maintainig > >>> two separate kernels is big hassle. > >>> > >>> So a small set of people who run into issue, would need to change kernel > >>> command line "crashkernel=128M@64M" or something similar. > >>> > >> > >> Do we have actual testing for how high the 64-bit kernel will load? > > > > I will do some experiments on my box today and let you know. > > if bzImage is used, it is 896M.
Strangely on my x86_84 systems with 37-rc6, I am trying to reserve memory and nothing shows up on /proc/iomem. dmesg says that I am reaserving 128M at 64M but nothing in /proc/iomeme. Going back to .36 kernel and see what happens.
Ok, last time we had looked that kexec-tools had constraint to load bzImage and initrd below 896MB and it must be coming from that.
> > or crashkernel=... will take two ranges like one high and one low. > > also kexec bzImage in 64bit should use startup_64 aka 0x200 offset instead of startup_32 in arch/x86/boot/compressed/head_64.S > > then bzImage can be put above 4G...
Neil had been trying that but AFAIK, he had no success. I don't know but he was struggling with setting up pages tables in kexec for 64bit startup.
But yes, making use of 64bit entry point is in the wish list.
Thanks Vivek
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